PERT Chart

Overview

A PERT Chart (otherwise known as a PERT Diagram) is a chart type realizes the Project Evaluation and Review Technique technology. It is applied mostly in large-scale projects where time is the major factor and allows to schedule a project without knowing precisely the details and durations of all activities. Find more information about PERT technology and using it in PERT Overview.

This article explains how to create a basic Pert Chart as well as configure settings that are specific to the type.

Pert Chart Data should be arranged as array of objects, where ID's of the tasks are necessary to be created. Extra data can be added if necessary. Read more about setting and managing the data in the PERT Data article.

Special Settings

Interactivity

Besides interactivity settings common for all charts, there is something special about PERT Charts events. The pointsSelect event returns such fields as selectedMilestones and selectedTasks, both fields contain all information about the milestones and tasks selected.

The following sample uses this event. Select milestones or tasks and watch the chart title.

Duration calculation

When the data is arranged, it is possible to set the exact duration for each task and the whole path. However, it is quite hard to evaluate time bounds of activities. To make an approximate calculation of the path duration, it is better to use three values: optimistic time (the shortest term which is necessary for an activity to be accomplished), pessimistic time (the longest term which is necessary for an activity to be accomplished) and the most likely time for the activity completion. There is a default formula used for the calculation, which you can find in the Terminology article. To rearrange the formula, use the expectedTimeCalculator() method.

Dummy Tasks

Dummy tasks are visual representations of dependencies between real tasks. Dummy task does not exist as a real task, does not affect the project duration (the duration of a dummy task equals 0) and connects milestones of real tasks for better visualization.

Dummy tasks have their own methods for appearance configuration: dummyFill() and dummyStroke(). There are no methods for dummy tasks in hover and selected states as they are not interactive.

Earliest and latest

Earliest and latest start and finish values are automatically calculated from the optimistic, pessimistic and most likely values or from duration value. These values are a good help in planning, as they show the most favorable and the worst time frames so they can be noticed in time and changed if critical.

The following sample shows how to demonstrate those values to watch them:

Slacks

There is a parameter all tasks named slack. Slack is a time period, which is actually wasted due to some reasons. For example, when a task can start only after another several tasks finish, the difference between the shortest task-predecessor and others are slacks. When slacks are detected, the best decision that can be made is to redistribute the resources from the task with shorter duration to the task with longer one.

The following example demonstrates the efficiency of the resources distribution due to the slacks existence.

Critical Path

Critical Path consists of milestones and tasks. If nothing special is set for the critical path, the visual settings of those elements will be taken from defaults. If you prefer to emphasize the critical path by changing the visual settings for its components, use the criticalPath() method.

Labels

Labels are text or image elements that can be placed anywhere on any chart (you can enable them on a whole series or in a single point). For text labels, font settings and text formatters are available.

Though, besides the colors and spacing, there are some special settings for the tasks' labels. Due to a specific shape, tasks have upper and lower labels, and it is possible to adjust both. Use the upperLabels() and lowerLabels() methods for it.

Tooltips

A Tooltip is a text box displayed when a point on a chart is hovered over. There is a number of visual and other settings available: for example, you can edit the text by using font settings and text formatters, change the style of background, adjust the position of a tooltip, and so on.

Statistics

There are two statistic values can be got from the Pert Chart: standard deviation and the critical path duration. Use getStat() method for both.